Thermal overload device

ABSTRACT

A polyphase circuit device using solder pot structures each controlling an independently operating actuating lever acting on an associating lever arm carried on rotatable shaft. A lever rotatable with the shaft operates a contact actuator to open a control circuit when a thermal overload occurs in any one conductor of the circuit being protected. A reset actuator is provided to permit reset when the overload has been removed.

United States Patent 1 Mouis [4 1 June 5, 1973 [54] THERMAL ()VERLOADDEVICE 3,118,990 1/1964 Jansson ..337/l88 3,284,596 11/1966 Barone"337/18! [75] Inventor: Louis Mouis, Aurora, [11.

73 Assi nee: Furnas Electric Com an B tavia, Primary Examiner-JamesTramme 1 g m v p a Attorney-McDougall, Hersh & Scott {22] Filed: July17, 1972 [57] ABSTRACT [21] Appl. No.2 272,132 A polyphase circuitdevice using solder pot structures each controlling an independentlyoperating actuating lever acting on an associating lever arm carried on[52] US. Cl. ..3l7/40 A, 317/40 A, 317/46, rotatable Shaft A leverrotatable with the Shaft 4 317/54 operates a contact actuator to open acontrol circuit [51] Int. Cl.....' ..H02h 5/04 when a thermal overloadoccurs in any one conductor Fleld of Search of the circuit beingprotected. A reset actuator is pro- 337/189; 317/114, 54, 40 A, 46 videdto permit reset when the overload has been removed. [56] ReferencesCited UNITED STATES PATENTS 7 Claims, 14 Drawing Figures 2,496,020l/1950 Pepper.....- ..3l7/40 A PATENTEB JUH 51973 sum 1 n7 4 PATENTEBJU"51915 3, 737, 727

sum u [1F 4 Pics. 10 8 THERMAL OVERLOAD DEVICE BACKGROUND OF THEINVENTION This invention relates generally to improved electricalcircuit protective devices. More specifically, it relates to devices forproviding thermal overload protection to polyphase electrical circuits.

It is known in the art that thermal overload protection may be providedby the use of so-called solder pots. See for instance the patent to D.Wilcox et al. issued Feb. 7, 1961. Solder pots consist of tubes orcylinders containing a quantity of solder in which is embedded a shaftheld from rotation when the solder is in a solid state. Carried on theend of the shaft is a ratchet for rotation with the shaft. A spring pawlengages the ratchet and is effective to prevent the movement of acontact actuator until the solder melts and permits movement of theratchet. A heating element connected in the electrical circuit to beprotected is disposed around the solder pot and, in the event of currentflow in excess of that desired, the heat produced by the heating elementis effective to melt the solder thereby permitting rotation of the shaftand ratchet carried thereon and consequently release of the switchactuator.

As stated; such devices have been in use for some time for connection toindividual conductors in order to protect the same against thermaloverload. With the advent of large electrical loads such as biggermotors, it has become increasingly necessary to use polyphase circuitsinstead of single phase circuits to supply these loads. Inasmuch asthermal overload protecting devices of the type described-possessnumerous advantages in particular situations, it would be advantageousto provide such a device for the protection of polyphase circuits.

Therefore, it is an object of this invention to provide a novel thermaloverload protection device for a polyphase circuit which utilizes theadvantages of the solder pot devices described.

It is another object of this invention to provide a ther- I BRIEFSUMMARY OF THE INVENTION The foregoing and other objects are achieved inone embodiment of the invention by the provision of a circuitcontrolling switch actuated by a rocker mounted on a shaft which carriesa number of lugs equal to the 'number of conductors in the circuit andwherein each lug engages with a separate-pawl normally held frommovement by a solder port but which are permitted movement when thesolder in any one pot has melted due to excess current flowing in anyone conductor so as to permit actuation of the rocker arm therebypermitting operation of the switch.

BRIEF DESCRIPTION OF THE DRAWINGS An understanding of the structure andmode of operation of the invention may be derived from the detaileddescription taken in conjunction with the drawings in which:

FIG. 1 is a top plan view of a thermal overload protective device inaccordance with the invention; FIG. 1A is a partial exploded view of thedevice of FIG. 1; FIG. 2 is a front view of the device shown in FIG. 1;FIG. 3 is a side view of the device shown in FIG. 1; FIG. 4 is a bottomview along the lines 44 of FIG.

FIG. 5 is a view along the lines 55 of FIG. 3; FIG. 6 is a view alongthe lines 66 of FIGS. 1 and 3;

FIG. 7 is a view along the lines 77 of FIG. 2 illustrating the mechanismin a normal or non-actuated position;

FIG. 8 is a view along the lines 8-8 of FIG. 2 illustrating themechanism in the normal or non-actuated position;

FIG. 9 is a view along the lines 99 of FIG. 2 illustrating the mechanismin the tripped or actuated posi-,

DETAILED DESCRIPTION The switch housing is best shown in FIGS. 1, 3, and4 wherein the numeral Zindicates the upper body portion of the switchand the numeral 4 indicates the lower body portion of the switch housingwhich is formed of any suitable plastic or similar insulating materialand has a plurality of ledges or supporting surfaces for a set ofincoming terminals 8 and a set of outgoing terminals 10. The incomingterminals 8 are electrically con nected by means of conductors 12 tofirst terminals 14 which are connected in turn to coiled electricallyconducting heating elements 16. The other end of each heating element 16is connected to a terminal 18 which in turn is connected to one of theoutgoing terminals 10. Thus in the embodiment illustrated connectionsare provided for each of three conductors in a polyphase circuit. Insuch a circuit therefore'any one conductor is connected to an incomingterminal 8 through a conducting element 12 to a terminal 14 through aheater 16, a terminal 18, and to an, outgoing tenninal 10. In thismanner a protective device in accordance with the invention may beconnected in a load circuit so as to respond to the current flowingtherein.

Connections for operating a circuit interrupting device such as acontactor are provided by a terminal 20 which is connected to a fixedcontact 22. The circuit is completed from the fixed contact 22 through amovable contact 24 to another fixed contact 26 which is connected to aterminal 28. Thus one end of the operating coil of a contactor may beconnected to the terminal 20, fixed contact 22, movable contact 24,fixed contact 26, and to the terminal 28 so as to be energized when thecontacts 22, 24 and 26 are in engagement with each other and bede-energized when these contacts do not engage.

As may best be seen in FIG. 6 the movable contact 24 is mounted in thelower housing 4 in a hollow extension 30 thereof and is urged toward thefixed contacts 22 and 26 by a coil spring 34 which bears against it andagainst the wall of the hollow extension. Thus the movable contactnormally completes a circuit between fixed contacts 22 and 26.

The switch actuating mechanism within the housing includes a reset lever36, a wedge 38 and an actuator 40. As will be described, the mechanismprovides for operation of the switch in the event of overload in any oneof the conductors being protected. For resetting purposes the actuator40 is reciprocated in a direction longitudinally of the same andcontacts directly with the wedge 38 which has camming engagement withthe reset lever 36 causing the lever to rotate and in turn causerotation of a shaft 42 extending transversely in the bottom of the lowerhousing 4. As may best be seen in FIGS. 6 and 7, the shaft 42 rotates ina trough 44 provided in the lower housing and is retained therein by apair of bars 46 held by threaded fasteners 48 in the lower housing andoverlying the shaft 42 and trough 44. Extending upwardly from the shaft42 are spaced lever arms 50, one for each conductor, provided with acamming surface 52. One such lever arm is provided to correspond witheach set of input and output terminals.

Disposed adjacent each lever arm 50 is an actuating lever 54 mounted forfree rotation on a shaft 56 extending transversely on the bottom of thelower housing substantially parallel to the shaft 42. Each actuatinglever is provided with a rearwardly extending projection 58 having aboss 60 formed thereon. Encompassing the boss 60 and extending betweenit and the base of the lower housing 4 is a coil spring 62 urging itsassociated actuating lever in the clockwise direction as shown forinstance in FIG. 11. Thus, assuming the actuating lever 54 is free tomove, its associated spring 62 extends to cause it to rotate in theclockwise direction. As it rotates about the shaft 56 it bears againstthe camming portion 52 of the lever arm 50 and consequently causes thatarm to rotate in the clockwise direction. The rotation of the shaft 42causes the reset lever 36 to rotate in the clockwise direction wherebyits free end camming against the interior surface 64 of the wedge 38moves the wedge downwardly as shown in FIG. 11. The downward movement ofthe wedge forces the actuator 40 which bears against the movable contact24 to move downwardly against the force of the coil spring 34interrupting the circuit between fixed contacts 22 and 26.

In order to maintain the device in its normal or nontripped position,each actuating lever 54 has attached thereto a leaf spring 66 attachedat one end to the lever 54 and having a free end 68 extending beyond thearm and provided with a bent or tooth portion 70. The spring 66 isconstructed so that it is biased toward the lever 54. This arrangementconstitutes a pawl in which the tooth portion 70 engages with the teethof a ratchet 72 comprising part of the solder pot construction.

The ratchet is fixed to a shaft 74 which extends within a barrel orsolder port 76. The barrel 76 is anchored in the upper housing 2 bymeans of a U-shaped collar 78 engaging near its bottom on one side of awall of the housing and a spring washer 80 engaging near its bottom onthe other side of that wall. The heating coil 16 surrounds the barrel 76and as described above is connected into the circuit. As is well known,in solder pot devices the shaft 74 is normally sealed to the barrel 76by eutectic solder which occupies the space befrom turning and the pawlconstituted by the spring 66 and its tooth will be held in its maximumcounterclockwise position (see FIG. 10) with the coil spring 62compressed. However, when an overload condition de velops, the heatingcoil 16 will melt the eutectic solder releasing shaft 74 and ratchet 72for rotation. The spring 62 will thereupon cause the actuating lever 54to rotate and operate the movable contacts 24 in the manner describedabove.

FIGS. 7 and 8 illustrate the device in the normal or non-trippedposition. Thus, in FIG. 7 the spring 66 has its tooth 70 engaged in theratchet 72 so that the lever 54 is maintained in its maximumcounterclockwise position and the coil spring 62 is compressed againstthe bottom of the lower housing 12. Under these circumstances the forceof the coil spring 34 is such as to maintain the movable contact in theupward position, as shown in these figures, completing a circuit betweenthe fixed contacts 22 and 26. At the same time, the

force of that spring transmitted to the actuator 40 through a pair oflegs 41 bearing against the movable contact 24 pushes the wedge 38upwardly as shown in that figure.

The cooperative movement between the actuator 40 and wedge 38 isachieved in the following manner:

The wedge (see FIG. 10) is provided with a ledge 82 and a beveled apron84. The actuator 40 has surfaces complimentary to those of the wedge.Thus the actuator is provided with a flat face 86 adapted to havecontact with the ledge 82 and a beveled edge 88 adapted to have cammingengagement with the apron 84. The flat face 86 and beveled edge 88 areformed on the body of the actuator 40, said actuator being additionallyprovided with the bifurcated legs 41. The actuator 40 is located betweenthe shoulders 92 formed on the inside of the housing and thus the bodyof the actuator will at all times have contact with those shoulders. Thebifurcated legs 41 have the additional function of accommodating thereset actuator and spring therefor, as will be presently described.

The fixed or stationary contacts of the switch previously identified as22 and 26 each consists of a member having an exterior portion 94 and aninterior depending portion 96 supported on a surface of the housing. Itwill be observed in FIG. 6 that the fixed contacts are spaced onrespective sides of the housing and accordingly the legs 41 of theactuator have a position between the contacts which permits the freemovement of those legs. The movable contact 24 is located within arecess 96 provided in the housing and the contact is freely movable in adirection to and from the depending portions of the fixed contacts so asto engage the same and thus control the opening and closing of theelectric circuit. The coil spring 34 'yieldingly forces the movablecontact 24 in an upward direction as shown in FIG. 6 and thus effects aclosing of the circuit unless the contact is maintained in open positionby the legs 41 of the ac tuator 40.

In order to reset the switch a reset actuator 98 is provided. Theactuator 98 is substantially rectangular in cross-section forapproximately its full length and is mounted for reciprocating movementwithin a passage 100 formed in the housing. The upper portion of theactuator 98 extends above'the housing for convenient access by theoperator. The bottom end of the actuator 98 is reduced in size and madecircular to form and end portion 102. The end portion provides a firstshoulder 104 and above the same a second shoulder 6 is provided on theactuator. The shoulder 104 engages with a coil spring 108 which looselysurrounds the end 102 and is confined between the shoulder 104 and thebottom of the lower housing 4 in a recess 110 provided for that purpose.The spring 104 thus yieldingly forces the actuator 98 upwardly until athird shoulder 1 12 engages an abutment 114 provided on the interior ofthe upper housing portion 2. The circular end 102 and a part of the coilspring 108 extend between the legs 41 of the actuator wherein the spacebetween these legs is made wide enough so as to receive the structurewithout interference as respects the movement of either part.

With this understanding of the elements of the switch and their relativedisposition, its operation may now be described.

Assuming that the switch contacts are closed by engagement of themovable contact 24 with the depend ing portions of the stationarycontacts 22 and 26 (see FIGS. 7 and 8), it will be seen that theactuating levers 54 are held in retracted position against the force oftheir associated springs 62 by engagement of their respective teeth 70with their associated ratchet wheels 72. In this position of theactuating levers the wedge 38 and contacts 40 are free but are retainedin proper assembled position because the legs 41 of the actuator extendbetween the shoulders 92 and are biased by the spring 34. The contactsof the switch will thus maintain a closed circuit position until andoverload condition exists.

The overload condition will heat the coil 16 and eventually the eutecticsolder in the barrel 76 will melt to release the shaft 74. The ratchet72 is now free to ro-.

tate and such action takes place to release any one of the actuatinglevers 54 for movement in a clockwise direction (see FIG. 11) as aresult of the force asserted by its coil spring 62. The actuating lever54 upon rotating engages with the camming surface 52 of its associatedlever arm 50 to rotate it and thereby the shaft 42 in thecounterclockwise direction. With the rotation of the shaft 42 the resetlever 36 rotates in the clockwise direction and causes the wedge 38 tomove downwardly (see FIGS. 9 and 11). The ledge 82 bearing against theflat surface 86 of the actuator causes it to move downwardly whereby thelegs 41 effect an opening action of the movable contact 34. The switchcontacts have now been tripped bythe overload condition existing in anyone of the conductors constituting the electrical circuit beingprotected.

It should be noted at this point that the tripping acbe depressed by anoperator for depression of the reset actuator does not interfere withthe freedom of the actuator 40 to move.

For resetting purposes the operator depresses the reset actuator movingthe same downwardly against the force of the spring 108. When sodepressed, the shoulder 106 will contact the body of the actuator 40since the actuator is now confined between the wedge and the movablecontact having a location in its extreme bottom position (see FIG. 9) asthe result of which the front of the actuator is in engagement with theshoulders 92. Downward movement of the reset actuator will move theactuator 40 in a downward direction so that the surface 88 of theactuator will cam on the surface tion will occur even through the resetactuator 98 may I 84 of the wedge and cause the wedge to move upwardlyas shown in the drawings due to the coaction of the beveled edge 88 withthe beveled apron 84. If the overload condition has been relieved, theratchet 72 will be held against the rotation and relatching of thespring pawl 66 with the ratchet wheel is effected. The actuating lever54 which had previously been released is thereby again held in aretracted position. However, as long as the reset actuator is helddepressed, the switch contacts are maintained in open position and isfurther noted that should the overload condition still exist, then uponrelease of the reset actuator the contacts will still be maintained inan opened condition. Thus the switch contacts are permitted to closeupon release of the reset actuator only in the event the overloadconditions have been corrected.

Obviously various modifications may be made without departing from thescope of the invention and it is intended by the claims appended heretoto claim all such modifications and variations as fall within theirscope.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. Apparatus for protecting polyphase circuits against thermal overloadcomprising: a support structure; a plurality of incoming terminalsmounted on said support structure, each for independent connection to aseparate conductor forming a part of a polyphase electrical supplysystem; a plurality of outgoing terminals mounted on said supportstructure and spaced from said incoming terminals; electricallyconducting heating elements each separately connected from one of saidincoming terminals to one of said outgoing terminals; a pair of controlterminals mounted on said support structure; a movable contact elementfor connecting one control terminal to the other control terminal; biasmeans urging said movable contact element in a first direction; acontact actuator movably mounted in said support structure and engagingsaid movable contact element to cause movement of said movable contactelement against the force asserted by said bias means; a plurality ofactuating levers, one for each conductor in a circuit to be protected; aspring pawl mounted on each said actuating lever; a ratchet disposedadjacent each of 'said spring pawls; means normally restraining each ofsaid ratchets to prevent movement of its associated spring pawl andactuating lever; and operating means connected between each of saidactuating levers and said contact actuator to cause movement of saidcontact actuator in the event of movement of any of said actuatinglevers and to cause consequent movement of said movable contact elementto interrupt the circuit between said control terminals.

2. The apparatus of claim 1 including: a reset actuator comprising aplunger having a portion extending outwardly of said support structureand a portion within said support structure engageable with said contactactuator; bias means urging said reset actuator outwardly, said resetactuator when depressed against said bias means engaging said contactactuator to move it and cause movement of said operating means andconsequent movement of any one of said actuating levers which may havebeen released for movement by the existence of an overload in itsassociated conductor.

3. The apparatus of claim 1 wherein said operating means comprises arotatable shaft mounted in said support structure; a plurality of leverarms spaced along said shaft for rotation therewith, one disposedadjacent each of said actuating levers for engagement therewith; a resetlever mounted on said shaft for rotation therewith; and a movable hollowwedge mounted over said reset lever and engaging said contact actuator.

4. The apparatus of claim 1 wherein said means normally restraining eachof said ratchets comprises a hollow tube, a shaft extending into saidtube supporting a ratchet on an end thereof, and a quantity of hardenedsolder interposed between said shaft and said tube to prevent said shaftfrom rotating in said tube,

5. The apparatus of claim 4 wherein each tube is encompassed by one ofsaid electrically conducting heating elements so as to melt the solderto free said shaft for rotation in the event of an overload in thecircuit to be protected.

6. The apparatus of claim 5 including: a reset actuator comprising aplunger having a portion extending outwardly of said support structureand a portion within said support structure engageable with said contactactuator; bias means urging said reset actuator outwardly, said resetactuator when depressed against said bias means engaging said contactactuator to move it and cause movement of said operating means andconsequent movement of any one of said actuating levers which may havebeen released for movement by the existence of an overload in itsassociated conductor.

7. The apparatus of claim 6 wherein said operating means comprises arotatable shaft mounted in said support structure; a plurality ofleverarms spaced along said shaft for rotation therewith, one disposedadjacent each of said actuating levers for engagement therewith; a resetlever mounted on said shaft for rotation therewith; and a movable hollowwedge mounted over said' reset lever and engaging said contact actuator.

1. Apparatus for protecting polyphase circuits against thermal overloadcomprising: a support structure; a plurality of incoming terminalsmounted on said support structure, each for independent connection to aseparate conductor forming a part of a polyphase electrical supplysystem; a plurality of outgoing terminals mounted on said supportstructure and spaced from said incoming terminals; electricallyconducting heating elements each separately connected from one of saidincoming terminals to one of said outgoing terminals; a pair of controlterminals mounted on said support structure; a movable contact elementfor connecting one control terminal to the other control terminal; biasmeans urging said movable contact element in a first direction; acontact actuator movably mounted in said support structure and engagingsaid movable contact element to cause movement of said movable contactelement against the force asserted by said bias means; a plurality ofactuating levers, one for each conductor in a circuit to be Protected; aspring pawl mounted on each said actuating lever; a ratchet disposedadjacent each of said spring pawls; means normally restraining each ofsaid ratchets to prevent movement of its associated spring pawl andactuating lever; and operating means connected between each of saidactuating levers and said contact actuator to cause movement of saidcontact actuator in the event of movement of any of said actuatinglevers and to cause consequent movement of said movable contact elementto interrupt the circuit between said control terminals.
 2. Theapparatus of claim 1 including: a reset actuator comprising a plungerhaving a portion extending outwardly of said support structure and aportion within said support structure engageable with said contactactuator; bias means urging said reset actuator outwardly, said resetactuator when depressed against said bias means engaging said contactactuator to move it and cause movement of said operating means andconsequent movement of any one of said actuating levers which may havebeen released for movement by the existence of an overload in itsassociated conductor.
 3. The apparatus of claim 1 wherein said operatingmeans comprises a rotatable shaft mounted in said support structure; aplurality of lever arms spaced along said shaft for rotation therewith,one disposed adjacent each of said actuating levers for engagementtherewith; a reset lever mounted on said shaft for rotation therewith;and a movable hollow wedge mounted over said reset lever and engagingsaid contact actuator.
 4. The apparatus of claim 1 wherein said meansnormally restraining each of said ratchets comprises a hollow tube, ashaft extending into said tube supporting a ratchet on an end thereof,and a quantity of hardened solder interposed between said shaft and saidtube to prevent said shaft from rotating in said tube.
 5. The apparatusof claim 4 wherein each tube is encompassed by one of said electricallyconducting heating elements so as to melt the solder to free said shaftfor rotation in the event of an overload in the circuit to be protected.6. The apparatus of claim 5 including: a reset actuator comprising aplunger having a portion extending outwardly of said support structureand a portion within said support structure engageable with said contactactuator; bias means urging said reset actuator outwardly, said resetactuator when depressed against said bias means engaging said contactactuator to move it and cause movement of said operating means andconsequent movement of any one of said actuating levers which may havebeen released for movement by the existence of an overload in itsassociated conductor.
 7. The apparatus of claim 6 wherein said operatingmeans comprises a rotatable shaft mounted in said support structure; aplurality of lever arms spaced along said shaft for rotation therewith,one disposed adjacent each of said actuating levers for engagementtherewith; a reset lever mounted on said shaft for rotation therewith;and a movable hollow wedge mounted over said reset lever and engagingsaid contact actuator.